If energy is used at a rate of 20.0 J/s in an electric
circuit what is the power developed

20watts

Explanation:

Formula for calculating power is expressed as;

Power = Work done/Time

Note that the unit of workdone is Joules

Unit of Time is seconds

Hence the unit of power is Joules/seconds or J/s

Hence if the rate at which energy is used up is 20.0J/s, the power will also be 20J/s or 20watts since they have the same unit.